Question

Stone is vertically thrown upward with an initial velocity 55m/s. Find
a) the maximum height reached by the stone. b) Total time it takes to reach the ground.

Answer 1

Answer:

a) 151.25 m

b) 11 sec

.

Explanation:

Given,

g = -10 m/s²

u = 55 m/s

v = 0

.

a)

We know that,

v² - u² = 2gh

=> 0² - 55² = 2(-10)h

=> -55² = - 20 h

=> 55² = 20h

=> h = 55²/20

= 3025/20

= 151.25 m

.

b)

We know that,

v = u + gt

=> 0 = 55 + (-10)t

=> 10t = 55

=> t = 55/10

= 5.5 sec

Therefore,

time taken to reach max height = t = 5.5 sec

Now,

We know that,

Time taken to reach ground from max height = time taken to reach max height = 5.5 sec

Therefore,

total time taken = 2 × 5.5 = 11 sec

.

P.S.

answers will vary a bit if you consider g = -9.8 m/s²

.

Hope this helps :)